上一篇文章Android实战简易教程-第五十三枪（通过实现OnScrollListener接口实现上拉加载更多功能）讲述了如何实现上拉加载更多的功能，本篇，我们在上一篇的基础上实现下拉刷新功能。主要通过对滚动状态和手势监听实现这一功能，下面我们看一下代码：
1.header.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="10dip"
android:paddingTop="10dip" >
<LinearLayout
android:id="@+id/layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:id="@+id/tip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="下拉可以刷新！" />
<TextView
android:id="@+id/lastupdate_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<ImageView
android:id="@+id/arrow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="@id/layout"
android:layout_marginRight="20dip"
android:src="@drawable/pull_to_refresh_arrow" />
<ProgressBar
android:id="@+id/progress"
style="?android:attr/progressBarStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="@id/layout"
android:layout_marginRight="20dip"
android:visibility="gone" />
</RelativeLayout>
</LinearLayout>package com.example.listviewscrolldemo;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
public class LoadListView extends ListView implements OnScrollListener {
private int lastVisibleItem;// 最后一个可见项
private int totalItems;// 所有项
private int firstVisibleItem;// 第一可见项
private View footer, header;// 底部布局
private Boolean isLoading = false;
private Boolean isRemark = false;// 判断在当前页面的最顶端并下滑；
private int startY;// Y坐标值
private ILoadListener iListener;
private RLoadListener rListener;
private int scrollState;// 当前滚动状态；全局变量
private int headerHeight;// 顶部布局文件的高度；
final int NONE = 0;// 正常状态；
final int PULL = 1;// 提示下拉状态；
final int RELESE = 2;// 提示释放状态；
final int REFLASHING = 3;// 刷新状态；
private int state;// 判断当前状态
public LoadListView(Context context) {
super(context);
initView(context);
}
public LoadListView(Context context, AttributeSet attrs) {
super(context, attrs);
initView(context);
}
public LoadListView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initView(context);
}
/**
* 添加底部加载提示到布局Listview
*
* @param context
*/
private void initView(Context context) {
LayoutInflater inflater = LayoutInflater.from(context);
footer = inflater.inflate(R.layout.footer, null);
header = inflater.inflate(R.layout.header_layout, null);
footer.findViewById(R.id.ll_footer).setVisibility(View.GONE);// 首先设置加载提示不可见
measureView(header);
headerHeight = header.getMeasuredHeight();
Log.i("tag", "headerHeight = " + headerHeight);
topPadding(-headerHeight);
this.addFooterView(footer);
this.addHeaderView(header);
this.setOnScrollListener(this);// 设置滚动监听
}
/**
* 通知父布局，占用的宽，高；
*
* @param view
*/
private void measureView(View view) {
ViewGroup.LayoutParams p = view.getLayoutParams();
if (p == null) {
p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
}
int width = ViewGroup.getChildMeasureSpec(0, 0, p.width);
int height;
int tempHeight = p.height;
if (tempHeight > 0) {
height = MeasureSpec.makeMeasureSpec(tempHeight, MeasureSpec.EXACTLY);
} else {
height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
view.measure(width, height);
}
/**
* 设置header 布局 上边距；
*
* @param topPadding
*/
private void topPadding(int topPadding) {
header.setPadding(header.getPaddingLeft(), topPadding, header.getPaddingRight(), header.getPaddingBottom());
header.invalidate();
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
this.scrollState = scrollState;
if (lastVisibleItem == totalItems && scrollState == SCROLL_STATE_IDLE) {
if (!isLoading) {// 判断不是正在加载！
footer.findViewById(R.id.ll_footer).setVisibility(View.VISIBLE);// 首先设置加载提示可见
iListener.onLoad();
isLoading = true;
}
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
this.lastVisibleItem = firstVisibleItem + visibleItemCount;
this.totalItems = totalItemCount;
this.firstVisibleItem = firstVisibleItem;
}
// 传递
public void setInterface(ILoadListener iListener) {
this.iListener = iListener;
}
public void setRefreshInterface(RLoadListener rListener) {
this.rListener = rListener;
}
/**
* 加载更多数据的回调接口
*
* @author Administrator
*
*/
public interface ILoadListener {
public void onLoad();
}
/**
* 下拉刷新回调接口
*
* @author Administrator
*
*/
public interface RLoadListener {
public void onRefresh();
}
// 加载完毕
public void loadCompleted() {
isLoading = false;
footer.findViewById(R.id.ll_footer).setVisibility(View.GONE);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN://下拉
if (firstVisibleItem == 0) {
isRemark = true;
startY = (int) ev.getY();
}
break;
case MotionEvent.ACTION_MOVE://移动
onMove(ev);
break;
case MotionEvent.ACTION_UP://上拉
if (state == RELESE) {
state = REFLASHING;
// 加载最新数据；
reflashViewByState();
rListener.onRefresh();
} else if (state == PULL) {
state = NONE;
isRemark = false;
reflashViewByState();
}
break;
}
return super.onTouchEvent(ev);
}
/**
* 判断移动过程操作；
*
* @param ev
*/
private void onMove(MotionEvent ev) {
if (!isRemark) {
return;
}
int tempY = (int) ev.getY();
int space = tempY - startY;
int topPadding = space - headerHeight;
switch (state) {
case NONE:
if (space > 0) {// 向下滑动
state = PULL;
reflashViewByState();
}
break;
case PULL:
topPadding(topPadding);
if (space > headerHeight + 30 && scrollState == SCROLL_STATE_TOUCH_SCROLL) {// 如果正在滚动切超过30
state = RELESE;
reflashViewByState();
}
break;
case RELESE:
topPadding(topPadding);
if (space < headerHeight + 30) {
state = PULL;
reflashViewByState();
} else if (space <= 0) {
state = NONE;
isRemark = false;
reflashViewByState();
}
break;
}
}
/**
* 根据当前状态，改变界面显示；
*/
private void reflashViewByState() {
TextView tip = (TextView) header.findViewById(R.id.tip);
ImageView arrow = (ImageView) header.findViewById(R.id.arrow);
ProgressBar progress = (ProgressBar) header.findViewById(R.id.progress);
RotateAnimation anim = new RotateAnimation(0, 180, RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
anim.setDuration(500);
anim.setFillAfter(true);
RotateAnimation anim1 = new RotateAnimation(180, 0, RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
anim1.setDuration(500);
anim1.setFillAfter(true);
/**
* 四种状态
*/
switch (state) {
case NONE:
arrow.clearAnimation();
topPadding(-headerHeight);
break;
case PULL:
arrow.setVisibility(View.VISIBLE);
progress.setVisibility(View.GONE);
tip.setText("下拉可以刷新！");
arrow.clearAnimation();
arrow.setAnimation(anim1);
break;
case RELESE:
arrow.setVisibility(View.VISIBLE);
progress.setVisibility(View.GONE);
tip.setText("松开可以刷新！");
arrow.clearAnimation();
arrow.setAnimation(anim);
break;
case REFLASHING:
topPadding(50);
arrow.setVisibility(View.GONE);
progress.setVisibility(View.VISIBLE);
tip.setText("正在刷新...");
arrow.clearAnimation();
break;
}
}
/**
* 获取完数据；
*/
public void reflashComplete() {
state = NONE;
isRemark = false;
reflashViewByState();
TextView lastupdatetime = (TextView) header.findViewById(R.id.lastupdate_time);
SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
Date date = new Date(System.currentTimeMillis());
String time = format.format(date);
lastupdatetime.setText(time);
}
}
final int NONE = 0;// 正常状态；
final int PULL = 1;// 提示下拉状态；（下拉距离比较短，此时松开不刷新）
final int RELESE = 2;// 提示释放状态；（下拉距离较长，此时松开刷新）
final int REFLASHING = 3;// 刷新状态；（松开状态，正在刷新）
这四种状态决定了header布局的不同展示效果，具体由reflashViewByState()方法实现。
onMove()方法通过判断移动过程，实现四种状态之间的转换。
package com.example.listviewscrolldemo;
import java.util.ArrayList;
import java.util.List;
import com.example.listviewscrolldemo.LoadListView.ILoadListener;
import com.example.listviewscrolldemo.LoadListView.RLoadListener;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.ArrayAdapter;
public class MainActivity extends Activity implements ILoadListener, RLoadListener {
private LoadListView mListView;
private ArrayAdapter<String> adapter;
private List<String> datas;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
initDatas();
}
private void initDatas() {
for (int i = 1; i < 21; i++) {
datas.add("数据" + i + "");
}
}
private void initMoreDatas() {
for (int i = 1; i < 3; i++) {
datas.add("新数据" + i + "");
}
}
private void initViews() {
mListView = (LoadListView) findViewById(R.id.lv_main);
mListView.setInterface(this);
mListView.setRefreshInterface(this);
datas = new ArrayList<String>();
adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, datas);
// adapter=new
// ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1);
mListView.setAdapter(adapter);
}
@Override
public void onLoad() {
// 添加延时效果
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
public void run() {
initMoreDatas();// 获取更多数据
adapter.notifyDataSetChanged();// 刷新ListView
mListView.loadCompleted();// 隐藏加载提示
}
}, 2000);
}
@Override
public void onRefresh() {
// 添加延时效果
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
public void run() {
initRefreshDatas();// 获取更多数据
adapter.notifyDataSetChanged();// 刷新ListView
mListView.reflashComplete();// 隐藏刷新提示
}
}, 2000);
}
private void initRefreshDatas() {
// datas.add("新数据" + i + "");
datas.add(0, "下拉刷新数据" + 1 + "");//此方法插入表头
datas.add(0, "下拉刷新数据" + 2 + "");
}
}
届时，上拉加载和下拉刷新功能都实现了。
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版权声明：本文为博主原创文章，未经博主允许不得转载。
Android实战简易教程-第五十四枪（通过实现OnScrollListener接口实现下拉刷新功能）
原文地址：http://blog.csdn.net/yayun0516/article/details/48225023
